1. Field of the Invention
This invention relates to an auxiliary switch for indicating the condition of a circuit-interrupting device, and more particularly, to an electro-mechanical switch which senses the condition of both a circuit-interrupting device and its operating mechanism and gives sensible information concerning the condition thereof so that an operator of the circuit-interrupting device can determine what action is required.
2. Description of the Prior Art
Various types of high-voltage circuit-interrupting devices are well known. Such devices include fuses, circuit breakers, and circuit-switchers. Circuit-switchers comprise a family of circuit-interrupting devices, each of which includes an interrupting unit.
The interrupting unit generally includes one or more pairs of interrupting contacts which are normally engaged to conduct current through the interrupting unit, but which may be rapidly separated. Such separation is generally effected in an arc-extinguishing environment, which typically includes a quantity of dielectric fluid, such as SF.sub.6 gas. As the contacts separate to elongate the arc forming therebetween, such elongation and the action of the dielectric gas extinguish the arc to effect current interruption within the interrupting unit. Typically, the gas may be "puffed" at the arc to aid in this circuit interruption.
The contacts are rapidly separated by a stored-energy mechanism, which typically includes a robust spring which is normally compressed to bias the contacts to an open position. The stored-energy mechanism is normally latched to prevent the release if the energy stored in the spring and to maintain the contacts in their normal engaged condition. Typically in circuit-switchers, the latch may be operated to release the energy stored in the spring in response to one of two types of conditions. First, the energy may be released by operation of a "shunt trip" mechanism in response to the detection by appropriate sensors of untoward circuit conditions, such as overcurrents, fault currents, short-circuit currents, overpressure in a transformer, or improper differential currents. As an adjunct to such sensors, the shunt trip mechanism may also be operated by a remote operating switch, which causes the interrupting unit to interrupt magnetizing or normal current in the circuit. This latter operation of the circuit-interrupting device may be effected in order to perform maintenance on the circuit, on the device itself, or for any other reason requiring interruption of the circuit for reasons other than faults or the like.
The stored energy may also be released in typical circuit-switchers in response to manual manipulation of a manual operating mechanism associated with the stored-energy mechanism. Typically, and similar to the operation of the circuit-interrupting device in response to remote control signals in other than fault situations, it may be desirable to operate the interrupting device, and to therefore interrupt the circuit, by manual manipulation of the manual operating mechanism for reasons related to maintenance, repair, or testing of either the circuit or the circuit-interrupting device.
A species of circuit-switcher is a device in which the interrupting unit may be operated, as described above, but which may not be automatically reset; that is, may not have its interrupting contacts automatically reclosed following separation thereof. In this type of device, whether the interrupting contacts are separated or opened due to either operation of the latch by a remote sensor or by manipulation of the manual operating mechanism, the contacts may be re-engaged only by appropriate manipulation of the operating mechanism. Since the interrupting unit is of the type wherein, once the contacts are separated or opened, closure of those contacts automatically re-stores energy to the stored-energy mechanism as well as latches this mechanism against the release of energy, the above-referred-to manipulation of the manual operating mechanism involves the rotation of a handle or the like by a worker to reclose the contacts following the opening thereof. Such reclosure of the contacts, as already stated, re-stores energy to the stored-energy mechanism.
In a specific embodiment of this species of circuit switcher, the handle of the manual operating mechanism may be rotated from a "home" position to a "trip" position to release the stored energy and to thereby open the interrupting contacts. Further rotation of the handle, in the same direction, from the "trip" position to a "reset" position recloses the contacts and re-stores energy in the stored-energy mechanism. The return of the handle from the "reset" position to the "home" position has no effect on the interrupting contacts. If the interrupting contacts have been initially separated due to the operation of the shunt-trip device in response to the action of the remote sensors, the initial movement of the handle from the "home" position to the "trip" position has no effect on the open contacts; however, further rotation of the handle from the "trip" position to the "reset" position is still necessary to reclose the interrupting contacts.
The interrupting units of circuit-switchers and related devices generally have a contact-indicating mechanism thereon. This mechanism indicates whether the interrupting contacts are opened or closed. However, in many environments, these interrupting devices are mounted on pedestals or structures which elevate them substantially above the ground. This elevation often renders it quite difficult for a ground-level worker to accurately determine the condition--opened or closed--of the interrupting contacts. Since the interrupting contacts and the other internal structure of the interrupting units are totally enclosed within an opaque insulative housing, it therefore becomes imperative for the worker to be able to accurately determine the condition of the interrupting units of the circuit-interrupting device in order to determine what action, if any, is necessary. The auxiliary switch of the present invention makes such accurate determination of the condition of the circuit-interrupting device possible. The auxiliary switch of the present invention also permits other devices to operate or be operated in accordance with the condition of the interrupting unit of the device as will hereinafter be made clear.